Hall, Charles Martin

SUBJECT AREA: Metallurgy

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b. 6 December 1863 Thompson, Ohio, USA

d. 27 December 1914 USA

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American metallurgist, inventor of the first feasible electrolytic process for the production of aluminium.

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The son of a Congregationalist minister, Hall was educated at Oberlin College. There he was instructed in chemistry by Professor F.F.Jewett, a former student of the German chemist Friedrich Wöhler, who encouraged Hall to believe that there was a need for a cheap process for the manufacture of aluminium. After graduating in 1885, Hall set to work in his private laboratory exploring the method of fused salt electrolysis. On Wednesday 10 February 1886 he found that alumina dissolved in fused cryolite "like sugar in water", and that the bath so produced was a good conductor of electricity. He contained the solution in a pure graphite crucible which also acted as an efficient cathode, and by 16 February 1886 had produced the first globules of metallic aluminium. With two backers, Hall was able to complete his experiments and establish a small pilot plant in Boston, but they withdrew after the US Patent Examiners reported that Hall's invention had been anticipated by a French patent, filed by Paul Toussaint Héroult in April 1886. Although Hall had not filed until July 1886, he was permitted to testify that his invention had been completed by 16 February 1886 and on 2 April 1889 he was granted a seventeen-year monopoly in the United States. Hall now had the support of Captain A.E. Hunt of the Pittsburgh Testing Institute who provided the capital for establishing the Pittsburgh Reduction Company, which by 1889 was selling aluminium at $1 per pound compared to the $15 for sodium-reduced aluminium. Further capital was provided by the banker Andrew Mellon (1855–1937). Hall then turned his attention to Britain and began negotiations with Johnson Matthey, who provided land on a site at Patricroft near Manchester. Here the Aluminium Syndicate, owned by the Pittsburgh Reduction Company, began to produce aluminium in July 1890. By this time the validity of Hall's patent was being strongly contested by Héroult and also by the Cowles brothers, who attempted to operate the Hall process in the United States. Hall successfully sued them for infringement, and was confirmed in his patent rights by the celebrated ruling in 1893 of William Howard Taft, subsequently President of the USA. In 1895 Hall's company changed its name to the Pittsburgh Aluminium Company and moved to Niagara Falls, where cheap electrical power was available. In 1903 a legal compromise ended the litigation between the Hall and Héroult organizations. The American rights in the invention were awarded to Hall, and the European to Héroult. The Pittsburgh Aluminium Company became the Aluminium Company of America on 1 January 1907. On his death he left his estate, worth about $45 million, for the advancement of education.

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Principal Honours and Distinctions

Chemical Society, London, Perkin Medal 1911.

Further Reading

H.N.Holmes, 1930, "The story of aluminium", Journal of Chemical Education. E.F.Smith, 1914, Chemistry in America.

ASD